Snap action circuit breaker

ABSTRACT

A snap action circuit breaker having encapsulating means such as a casing and a support secured within the encapsulating means. The support is designed to accommodate the components of circuit breakers such as the lead-in wires, snap blade and contact in predetermined fixed positions within the encapsulating means.

United States Patent Richard E. Perkins South Windham, Maine Appl. No.28l

Filed Jan. 2, 1970 Patented Nov. 9, 1971 Assignee Sylvania ElectricProducts Inc.

Inventor SNAP ACTION CIRCUIT BREAKER 1 Claim, 6 Drawing Figs.

U.S. Cl 200/168 G, 337/112,335/151 Int. Cl. H0lh 9/04 Field of Search200/168 6,

[56] References Cited UNITED STATES PATENTS 2,516,584 7/1950 Parr200/168 G X 2,870,287 1/1959 Corbitt, Jr. 200/168 G X 3,171,918 3/1965Killion 335/153 X 3,307,126 2/1967 Shaw et a1... 335/154 3,434,0793/1969 Ege,Jr 335/151 Primary Examiner-H. 0. Jones Attorneys-Norman J.OMalley and Owen J. Meegan ABSTRACT: A snap action circuit breakerhaving encapsulating means such as a casing and a support secured withinthe encapsulating means. The support is designed to accommodate thecomponents of circuit breakers such as the lead-in wires, snap blade andcontact in predetermined fixed positions within the encapsulating means.

PATENTEDunv 9 l97l 3,619,534

24 FIG.4

RICHARD E. PERKINS mv NTOR 8Y6 2 ATT RNEY SNAP ACTION CIRCUIT BREAKERBACKGROUND OF THE INVENTION 1. Field Of The Invention This inventionrelates to circuit breakers. More precisely, the invention disclosedherein relates to an improved snap action circuit breaker which istemperature and/or current sensitive and which can beemployed in knownmanners to control or provide protection for electrical circuits.

2. Description Of The Prior Art Circuit breakers, especially snap actiontype circuit breakers, are known products of commerce. The types bestknown essentially comprise a bimetallic, thermostatic strip or bladearranged in combination with suitable contact means so that contact canbe made or broken in response to predetermined conditions such asspecific current loads or temperatures. The blade and contact means arearranged within a conductive or nonconductive hermeticallysealed casingand the components are connected to lead-in wires which carry currentfrom some source external to the casing. In general, the strip or bladeis usually connected directly to one of the leadin wires. This lead-inwire blade assembly is normally suspended within the casing and arrangedoveranother contact connected to a second lead-in wire. The contact andthe second lead-in wire assembly may be-maintained in a fixed orsuspended position. Details relating .to snap action circuit breakerssimilar to the type to which the present invention pertains can befound-in U.S. Pat. Nos. 3,312,967 3,066,205, 2,978,556, 2,925,483 and2,424,909, all of which are incorporated herein byv reference.

Those skilled in the art-know that there are many outstanding problemsin the production of snap action circuit breakers. These problemschiefly arise by reason of the miniature size of the components involvedand the requirementthat such components be assembled and hermeticallysealed within a suitable encapsulating casing. For example, in manyexisting circuit breakers, the lead-in wires are especially fragile andeasily bent since they are oftentimes of an CD. of about 0.030inch. Theassembly of suchlead-in wires with the other components causes specialcomplications in view of .the fact that the straightness of the lead-inwires, the thickness of the welds involved in connecting the lead-inwires to the other components, e.g. the blade or the contact and thespacing of the lead-in wires, are all factors that can adversely affectthe precision and accuracy of the overall performance of the circuitbreaker. The effects of the above-mentioned factors are particularlydifficult to control when the encapsulating means involves a glasscasing or envelope.

SUMMARY OF THE INVENTION The present invention provides an improved snapaction circuit breaker of a unique structure which pennits simpleassembly and at the same time minimizes and permits effective controlover variations in such factors as lead-in wire bending, lead-in wirespacing and weld thickness, all of which can adversely afi'ect theperformance characteristics of the circuit breaker. Essentially, thesnap action circuit breaker of the present invention comprises a supportassembled in a fixed position withinencapsulating means such as a glasscasing or envelope. The support can be cast, formed, shaped or otherwiseassembled or a nonconductive material such as a ceramic and is designedto provide a capability for securing the lead-in wires in a fixed spacedapart position within the casing. For example, the support can providechannels which can closely accommodate the lead-in wires when insertedtherein or secured thereto by manners known to the art. When so securedin their respective fixed positions, one of the lead-in wires isoperationally connected to the snap blade such as by welding or thelike. The other lead-in wire is operationally connected to a contactwhich is also secured in a fixed position by the support in apredetermined relationship with the contact of the snap blade to providethe desired make or break response. In the preferred embodiment of thepresent invention, the lead-in DESCRIPTION OF THE PREFERRED EMBODIMENTThe preferred embodiments of the present invention will be betterunderstood by reference to the following drawings wherein:

FIG. 1 is a top view of a support of the present invention shownaccommodating lead wires, snap blade and a contact.

FIG. 2 is an elevational side view of the support of FIG. 1.

FIG. 3 is viewalong line 3-3.

FIG. 4 is a view along line 4-4.

FIG. 5 is a sectional top view of a snap action circuit breaker havingthe support of FIGS. 1-4 secured within a glass envelope.

FIG. 6 is a cross-sectional view along the line 6-6 of FIG. 5.

Referring now to FIG. 1-4, the support, molded of ceramic material isshown as 10 and has shoulders 30 and 40 respectively at opposite ends.A'first lead-in wire 12 extends axially through channel 1'22 (FIG. 3)and is secured in a fixed position as shown, such as by a holder bar 16.First lead-in wire 12 is operationally connected to snap blade 18 bywelding, brazing or the like. A second lead-in wire 14 extends axiallythrough shoulder 40 by way of channel 24 (FIG. 4) and is secured asshown in channel 24 bythe fixed contact 20. Fixed contact 20 issupported, on its edges, by the sides of the channel 24 and lead-in wire14. Second lead-in wire 14'is operationally connected (preferably byresistance welding) to contact 20which is secured in a fixed-position onsupport 10. Therelativeposition of contact 20 with respect to contact 19of blade 18 is determined inaccordance with theparticular-make or breakresponse desired between contacts 19 and 20.

Referring now to FIG. 5, the support and components of FIG. 1-4 areshown secured within. glass envelope 50 which is hermetically sealedabout the support. In one embodiment, the support can be secured withinthe envelope by bonding a surface of the-support, such as the bottomthereof, to a portion of the inner surface of the envelope by bondingmaterials and methods known to the art. Alternatively, as shown in FIG.6, the support 30 can be sufficiently large to abut against the walls ofthe envelope so thereby holding it firmly in place. The hermetic sealingof the envelope about the support and the lead-in wires can beaccomplished by manner known to the art.

The encapsulated snap action circuit breaker of FIG. 5 provides specialadvantages over those presently employed in the art, especially when thecircuit breakers of the present invention are employed as protectors oncircuits such as motor windings. Because of the high inductive voltagesinduced in motor windings, arc tracking can occur at the interfacebetween the snap blade, contact arm and lead-in wires of many of thesnap action circuit breakers known to the art. This arc tracking candestroy a circuit breaker in a short time. In the circuit breaker ofFIG. 5, however, arc tracking is effectively eliminated by reason of thefact that lead-in wires 12 and 14, snap blade 18 and contact 20 arearranged and maintained in fixed positions on support 10. Accordingly,as blade 18 opens, the spacing contacts 19 and 20 and therefore thespacing between lead-in wires 12-14 becomes progressively wider, therebyextinguishing the arc. This advantage is most effectively assured by thearrangement of the lead-in wires 12 and 14 shown in FIG [-5 wherein eachlead-in wire extends axially through opposite ends of the casing andthis arrangement of lead-in wires is definitely preferred. However, itis to be understood that the circuit breakers of the present inventioninclude other arrangements wherein, for example, the lead-in wires aresecured by the support in a fixed, spacedapart relationship but extendinto the casing from the same end.

By way of illustration only, the actual dimensions of a ceramic supportsimilar to that of HG. 1-4 are as follows:

overall length-1.06 inches; spaced-apart overall width-0.100 inch;

overall height at shoulders-0.240 inch;

height of shoulders0.060 inch;

ID. of channels 22 and 24-0062 inch;

length of channels 22-14/32 inches and 24 1 3/32 inches The lead-inwires inserted into channels 22 and 24 are Kovar (or No. 4 Alloy) andhave an CD. of 0.050 inch. The snap blade 18 is Chace No. l05lnvar-steel Alloy, contact 19 is coin silver-steel backed, welded to theblade which is welded to lead-in wire 12 by resistance weld. Contact 20was coin silver-steel backed 3/16 inches diameter X3/64 inches thick,and was operationally connected to lead-in wire 14 by resistancewelding. A circuit breaker of the type described above can operate inthe 35-50 ampere range.

As can be appreciated from FIGS. 1-4, the design of support provides acapability for maintaining the components of the snap action circuitbreaker in fixed relationships and also provides a convenient manner forintegrating or assembling the components. Bending of the lead-in wires,for example, is minimized and easily controlled. Also, the supportmaintains the lead-in wire, snap blade assembly in a fixed position andpermits only the blade to move. As mentioned, in prior art devices, thelead-in wires, blade assembly is usually suspended within theencapsulating means and the whole assembly moves in making or breakingcontact. This feature provides undesirable stain characteristics whichcan adversely affect the fragile assembly as well as the seal about thelead-in wire and casing. The feature also permits undesirable variationsbetween lead-in wire spacing to occur during operation.

Since certain changes may be made in the above product without departingfrom the spirit and scope of the invention involved, all mattercontained in the above description or shown in the accompanying drawingsshould be construed as illustrative and not in a limiting sense.

Having described the invention together with preferred embodimentsthereof, as well as manners of practicing same, what I declare as newand desire to secure by U.S. Letters Patent is as follows:

As my invention, I claim:

1. A snap action circuit breaker comprising: a tubular hermeticallysealed glass envelope; an elongated unitary insulative support disposedwithin said envelope, said support including a first longitudinal grooveat one end thereof and a second longitudinal groove at the other endthereof; a first leadin wire hermetically sealed through one end of saidenvelope and extending into said first groove; a second lead-in wirehermetically sealed through the other end of said envelope and extendinginto said second groove; a bimetallic snap-acting thermostatic elementlongitudinally disposed on said support, one end of said element beingwelded to the end of said first lead-in wire that is in said firstgroove; a first electrical contact disposed on the other end of saidelement; and a second electrical contact welded to the end of saidsecond lead-in wire that is in said second groove, said first and secondcontacts being normally closed, said first and second contacts openingupon actuation of said snap-acting element.

1. A snap action circuit breaker comprising: a tubular hermeticallysealed glass envelope; an elongated unitary insulative support disposedwithin said envelope, said support including a first longitudinal grooveat one end thereof and a second longitudinal groove at the other endthereof; a first lead-in wire hermetically sealed through one end ofsaid envelope and extending into said first groove; a second lead-inwire hermetically sealed through the other end of said envelope andextending into said second groove; a bimetallic snap-acting thermostaticelement longitudinally disposed on said support, one end of said elementbeing welded to the end of said first lead-in wire that is in said firstgroove; a first electrical contact disposed on the other end of saidelement; and a second electrical contact welded to the end of saidsecond lead-in wire that is in said second groove, said first and secondcontacts being normally closed, said first and second contacts openingupon actuation of said snap-acting element.